Based on recent advances in the synthesis of iron chelates which behave as reversible oxygen carriers it is proposed to synthesize a series of such compounds, designed to be compatible with their use as blood substitutes. Two approaches will be tried. Firstly and more simply to make a chelate compatible with a fluorocarbon emulsion. Secondly to make a compound that will have water solubility to be compatible with natural plasma. Both approaches will require a simple route to a pentacoordinate iron complex with steric encumbrance provided for the bound oxygen molecule. A series of binding studies will be undertaken to determine the factors which influence the pressure yields volume curve of such compounds. In vivo and in vitro testing of these compounds will be undertaken by Dr. R. P. Geyer of the Department of Nutrition, Harvard School of Public Health.